Manganese toxicity in epiphytic lichens: chlorophyll degradation and interaction with iron and phosphorus

Concentrations of chlorophylls a and b decreased with increasing MnCl2 supply in the zepiphytic lichen Hypogymnia physodes, but not in Lecanora conizaeoides. The reduction of chlorophyll concentrations in. H. physodes was as strong (chlorophyll a) or even; stronger (chlorophyll b) as in samples treated with CuCl2. FeCl3 compensated for MnCl2-induced chlorophyll degradation in H. physodes. Furthermore, MnCl2-induced growth inhibition of soredia cultivated on agar plates was alleviated by FeCl3. These results suggest that Mn causes intra cellular Fe deficiency in H. physodes. A soredia growth test with MnCl2 and KCl in combination proved that mitigating effects of FeCl3 were not just caused by reduced chemical activity of Mn2+ due to the addition of another salt. Furthermore, the test showed that Cl- did not inhibit soredia growth. High FeCl3 concentrations applied alone or in combination with MnCl2 were even more detrimental to H. physodes than MnCl2. MnCl2 did not affect the concentrations of ATP, ADP and AMP in H. physodes. This suggests that Mn uptake does not induce intracellular P deficiency in H. physodes despite that Mn is known to be immobilized with P in H. physodes in intracellular polyphosphate granules and in extracellular encrustations. (C) 2002 Elsevier Science B.V. All rights reserved.